Doctors say the number of people coming to A&E units with self-harm injuries is on the rise.
Sam now talks to other young people about self-harm and how to cope with it. She wrote her disturbing story for BBC News Online and explained how she broke the self-harm habit.
When I first began senior school, I found myself alone for the first time in two years, with no friends and only myself to depend on.
I thought that there would be so many people on their own like me and that it would be easy to make new friends.
How wrong I was.
I tried so hard, but it just didn't seem to work. I sat alone in many of my lessons.
At a size 12 to 14, and being taller than my peers, I realised I was developing quicker than them. At first I wasn't bothered.
Then, as I walked the corridors, people began shouting 'fatty' at me and making fun of basically everything.
One small childish comment changed my whole life: 'You smell'. It stuck and soon people were avoiding me in the corridors.
I went home every night and scrubbed myself in the shower until my skin was red.
The angrier I got, the more they enjoyed watching me. I was getting on the bus in the morning thinking I was going to throw up from fear.
I went home every night and scrubbed myself in the shower until my skin was red
One November it became so hard for me that I gave in and took an overdose of painkillers.
'Good - that will make them sorry', I thought before I drifted to sleep.
When I woke up in the morning I decided not to tell anyone, faking illness as a cover up.
But I really did want to die. My dad and the school found out about the overdose, and a few weeks later, as I sat in my bedroom, I suddenly became so angry that I grabbed a razor and began slicing at my wrists.
I hacked away for a long time before I realised that it made me feel better cutting at myself - so I moved the razor up my arm and cut there.
In a way, I saw what I was doing to my body as an art - I enjoyed watching the blood and seeing what patterns I could make.
Soon I was cutting myself so often it became habit. For every person that hurt me I cut myself a little more.
I would say their names aloud. Then cut.
I was careful to cover it up, although looking back, I think that people knew but just didn't say anything. Once, I had my wrists right through to my elbows bandaged.
In a way, I saw what I was doing to my body as an art - I enjoyed watching the blood and seeing what patterns I could make
I took four more overdoses, each time, more desperate, I pushed up the amount I was taking, regardless of the damage I was probably doing to my body.
On the fourth occasion, I was at home alone - I just sat there thinking.
I was involved at the time with Children's Express - a journalism project aimed at eight to 18 year olds.
When someone from the project rang that evening, he tried to calm me down, and for the first time, I cried about the whole situation.
'I don't want to die,' I sobbed down the line. That night, I wanted to change.
I was referred to both a counsellor at school, and to a child psychiatrist. I hated everything about the psychiatrist, but the counsellor helped me.
But I still found myself slipping deeper and deeper into depression. I just drew far away from any kind of relationship with anyone.
I cut myself nearly every day, in the toilets at school, at home, anywhere I could.
Sometimes I pulled my school tie around my neck until my lips turned blue
Other girls with similar problems approached me. One, who I'll call Rachael, was also bullied, and cut herself. We became friends.
Some mornings she came in with blood all over her wrists, and she hardly ever ate.
In the end, I experienced the same attitude that many people have about self-harmers: 'They can't be helped'. There seemed to be nothing that I could do.
I continued to self-harm, finding new ways, as cutting didn't seem to have the same effect anymore.
Sometimes I pulled my school tie around my neck until my lips turned blue, and I pulled scarves around my neck, holding them tight until the whole world seemed to spin.
Once, I stood at a train station willing myself to jump off the platform, then climbed a high-rise block, finding a gate barring access to the roof.
But finally I gave in and began to talk properly to the counsellor. I began telling her what I was feeling and about the bullying.
I was prescribed antidepressants, then pills for anxiety and to help me sleep.
I met my mum, who I hadn't seen since I was four - and it was the biggest step that I have had to make.
Breaking the cycle
It's been nearly a year now since I cut myself, and I'm glad I'm not trapped in that cycle any more.
I hope to work as a writer one day, and I'm taking AS levels and working with a mental health charity, Mind Out for Mental Health.
I read Sylvia Plath's poetry recently - which deals with issues such as depression and self-harm.
I think self-harm is one of the most difficult things a person can do to themselves - but I'd say to others in my situation that they can get to where they want to be, someday.
Everything I've experienced has just made me a stronger person.